Road paving is based on the application of a layer of asphalt mixture (asphalt surface course) that comprises asphalt, i.e. bituminous products obtained from petroleum and different types of stone materials (aggregates), such as course aggregates, for example, grinded stone material, and fine materials such as sand and dust, or other inorganic fillers. A typical paving asphalt mixture composition may contain about 54% course aggregates, about 35% fine aggregates, about 5% stone dust, and close to 6% asphalt or bitumen, which acts as a binding agent.
Traditional paving methods are called “hot” mix methods. These methods consist of mixing the aggregates with bituminous products at a high temperature, of between 130° C. and 180° C., followed by a placement and compaction process, also under hot conditions.
The so-called Warm Mix Asphalt methods are based on technologies developed in order to reduce the paving temperatures, i.e. the temperatures used in the preparation and application of asphalt surface courses. The basis for these technologies consists of reducing the asphalt viscosity in order to facilitate the mixing thereof with the aggregate, such that compaction of the mixture is effective at temperatures between 20° C. and 55° C. lower than those used in traditional methods. The most obvious advantage arising from reducing the roadway paving temperature is energy savings. Another clear benefit of these techniques is that they facilitate paving in places where heating equipment is not available in situ. In such places, the cooling that may take place during transport of the asphalt would lead to problems when conventional asphalt mixtures are used. On the other hand, Warm Mix techniques allow for a considerable reduction in the emission of toxic smokes, such as carbon monoxide, and nitrous and sulfurous oxides.
Warm Mix techniques basically require having additives that reduce the viscosity of the bituminous compounds. However, such additives will be considered completely effective if they also have an effect on the rest of the technical difficulties that asphalt additives must resolve, in relation to the application and the durability of asphalt. In sum, a suitable additive for the preparation of warm asphalt mixtures should provide a solution for 5 technical problems:                a) asphalt exhibits very high viscosities at temperatures between 100° C. and 160° C., which makes handling difficult at these temperatures.        b) asphalt at temperatures between 58° C. and 82° C. has the consistency of a viscous liquid.        c) asphalt at low temperatures may become too fragile.        d) asphalt reacts with environmental oxygen, which favours the aging thereof.        e) a high interfacial tension is generated between the asphalt and the aggregate, which causes adhesion problems.        
In order to resolve the technical problems described above, a large variety of bituminous compositions and application processes have been proposed.
The state of the art includes studies that propose using waxes with a high melting point, which makes it possible to reduce the manufacturing and placement temperature of the mixture by a few degrees. However, using these waxes increases the asphalt viscosity at low temperatures, making the asphalt fragile and brittle. Likewise, patent U.S. Pat. No. 6,588,974 relates to a bitumen or asphalt for the production of an asphalt surface course or asphalt mixture; the bitumen or asphalt contains a proportion of paraffin obtained by means of the Fischer-Tropsch synthesis process (FT paraffin). The invention relates to an asphalt or bituminous mixture and to a method for producing a corresponding road or roadway and/or a filler/coating with asphalt.
The state of the art also includes additives that comprise different types of copolymers. Thus, patent U.S. Pat. No. 4,818,367 relates to a composition for an asphalt mixture that contains a copolymer of olefin with anhydride or nitrile, and an unsaturated elastomer that contains at least two terminal groups, each with an active hydrogen, a halogen, an epoxy oxygen or a cyanocarbon. The composition may be prepared by copolymerizing an olefin with an anhydride or a nitrile in the presence of a free-radical initiator and, subsequently, mixing the copolymer with the asphalt and the elastomer. The copolymer may be initially mixed with a mixture of petroleum oil, then with the elastomer and, finally, with the asphalt. The copolymer may be a polyanhydride of maleic anhydride and 1-octadecane and the elastomer may be a terminal hydroxy-polybutadiene.
The state of the art also includes asphalt compositions that comprise amine-type emulsifiers. Thus, for example, patent JP 163100 discloses suitable liquid emulsifiers to prepare an asphalt emulsion that contain at least one amine compound selected from monoamines and polyamines, with between 8 and 22 carbon atoms in the aliphatic hydrocarbon group and at least one carboxylic acid, which is selected from saturated straight-chain carboxylic acids with an increasing number of carbon atoms; saturated branched-chain carboxylic acids with between 4 and 18 carbon atoms; unsaturated straight-chain carboxylic acids with between 12 and 18 carbon atoms; saturated carboxylic acids each containing a naphthene ring and between 5 and 18 carbon atoms; aromatic carboxylic acids each containing a benzene ring and between 7 and 18 carbon atoms; and dimer acids primarily composed of a dicarboxylic acid with 36 carbon atoms; the proportion by weight between the amine compound and the carboxylic acid ranges between 4/1 and 2/3.
Despite the inventions disclosed in the state of the art, there is still a need to obtain warm asphalt compositions that have mechanical properties similar to those of hot mixtures, and which exhibit a satisfactory behaviour in terms of compaction degree, adhesion and resistance to oxidation and fatigue.